[SCSI] sg: cap reserved_size values at max_sectors
This patch (as857) modifies the SG_GET_RESERVED_SIZE and
SG_SET_RESERVED_SIZE ioctls in the sg driver, capping the values at
the device's request_queue's max_sectors value. This will permit
cdrecord to obtain a legal value for the maximum transfer length,
fixing Bugzilla #7026.
The patch also caps the initial reserved_size value. There's no
reason to have a reserved buffer larger than max_sectors, since it
would be impossible to use the extra space.
The corresponding ioctls in the block layer are modified similarly,
and the initial value for the reserved_size is set as large as
possible. This will effectively make it default to max_sectors.
Note that the actual value is meaningless anyway, since block devices
don't have a reserved buffer.
Finally, the BLKSECTGET ioctl is added to sg, so that there will be a
uniform way for users to determine the actual max_sectors value for
any raw SCSI transport.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Acked-by: Douglas Gilbert <dougg@torque.net>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 65c6a3c..e83f1db 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -78,7 +78,9 @@
static int sg_get_reserved_size(request_queue_t *q, int __user *p)
{
- return put_user(q->sg_reserved_size, p);
+ unsigned val = min(q->sg_reserved_size, q->max_sectors << 9);
+
+ return put_user(val, p);
}
static int sg_set_reserved_size(request_queue_t *q, int __user *p)